It is known that polarized normal incidence spectrometry may be used for measuring line profiles' parameters being applied to one-dimensional (1D) line arrays (pattern) on an article by help of Rigorous Coupled-wave Theory (Further below RCWT) and the like modeling. The same approach can also be applied to two-dimensional (2D) line arrays or any other 2D periodic pattern (e.g. arrays of lines, pads, vias, etc.).
U.S. Pat. No. 6,665,070 discloses a metrology device with a rotatable polarizer that is calibrated to align the transmission axis of the polarizer with the axis of orientation of a sample, such as a diffraction grating. The axis of orientation of the diffraction grating can be either the TE or TM axis. The system offset angle between the transmission axis of the polarizer in its home position and an axis of motion of the stage, such as a polar coordinate stage, is determined. Whenever a new substrate is loaded onto the stage, the sample. offset angle between the axis of motion of the stage and the axis of orientation of a sample is measured. The polarizer offset angle, which is the angle between transmission axis of the polarizer and the axis of orientation of the sample, is the sum of the system offset angle and the sample offset angle. Thus, by rotating the polarizer by an amount equivalent to the sum of the system offset angle and the sample offset angle, the polarizer offset angle is reduced to zero. If desired, the polarizer may be rotated once to compensate for the system offset angle and then rotated to compensate for the sample offset angle for each newly loaded substrate or the polarizer may be rotated to compensate for both the system offset angle and the sample offset angle for each newly loaded substrate.
U.S. Pat. No. 6,657,736 discloses a method and system for determining a line profile in a patterned structure, aimed at controlling a process of manufacture of the structure. The patterned structure comprises a plurality of different layers, the pattern in the structure being formed by patterned regions and un-patterned regions. At least first and second measurements are carried out, each utilizing illumination of the structure with a broad wavelengths band of incident light directed on the structure at a certain angle of incidence, detection of spectral characteristics of light returned from the structure, and generation of measured data representative thereof. The measured data obtained with the first measurement is analyzed, and at least one parameter of the structure is thereby determined. Then, this determined parameter is utilized, while analyzing the measured data obtained with the second measurements enabling the determination of the profile of the structure.
According to the techniques of these patents, measurement of TE and TM polarization components is used that require a certain specific orientation of the polarizer's axis relative to the orientation of the line arrays on a patterned article. Usually, the polarizer's axis is orientated parallel to the line (TE polarization measurement) and/or perpendicular to the line (TM measurements).